What's a good way to clean up my migrations in Rails?

Remove the migration files once you've migrated your servers. If you ever want to start with a fresh deployment, run rake db:schema:load or rake db:setup. You shouldn't be re-running all your migrations as explained here.

You don't need to keep your migrations around forever, you are free to delete them as soon as you're sure you don't need them anymore. Just go into your db/migrate/ directory and delete the migrations that are older than, say, a couple months.

As long as all the migrations that you want to delete have been applied everywhere (i.e. development and production) then you don't need them anymore (unless you want to go backwards). Really, migrations aren't meant to be permanent files, they're just around to get you from A to B and then they're just baggage.

One way to go is to take a blank database and run all the migrations. Now you've got all the template data which you can save to a yaml. The yaml plus the schema should be enough to bring the DB back without running any of your previously existing migrations.

However, other answers should mention an existing tool or gem for doing this.